This replaces a small wood part in the extruder assembly and creates a guide between the drive gear and the hot end, eliminating jams inside the extruder. This fits the direct drive extruder upgrade (I bought it in October, 2013) that Printrbot sells for all models of their printers.
Print this part. Remove the lower front 3 mm screw holding your extruder together and remove the small wooden piece that forms the front of the filament channel between the drive gear and the hotend. Replace with this printed part. Check to see that the hole in the guide lines up with the hole in the hotend using some filament. The 3 mm screw hole came out tight on mine. It may help to ream this hole with a drill bit. The filament hole should be good for 1.75 mm filament without any rework.